This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Pathology services were provided to a variety of investigators both at the center and from outside institutions. Services included routine hematoxylin and eosin histology, molecular pathology (immunohistochemistry and in situ hybridization), electron microscopy, and histopathology consultation. In order to improve our diagnostic pathology capabilities, we systematically evaluate commercially available antibodies directed against human cells/tissues and infectious agents for application in the nonhuman primate species housed at the NEPRC. Antibodies are selected for potential applications in diagnostic and/or experimental pathology, and for reactivity in either snap-frozen or formalin-fixed, paraffin-embedded tissues. In addition, the Division of Comparative Pathology receives multiple requests each year to test antibodies and develop IHC protocols for investigators in our Division, other NEPRC Divisions, and collaborating investigators. The infection of Asian macaque monkeys with simian immunodeficiency virus (SIV) and SIV/HIV chimeric viruses (SHIVs) serves as an important animal model for studying the pathogenesis of HIV infection and AIDS. In addition, this model provides a challenge system for evaluating the efficacy of vaccines and antiretroviral agents designed to prevent infection or AIDS in humans. We have designed several molecular probes for localizing viral RNA in tissues of monkeys infected with various isolates and clones of SIV and SHIV. These probes are used to measure the quantity and distribution of infected cells in the tissues of infected monkeys. We also have probes that hybridize with target RNA or DNA sequences of several other viral pathogens, including HIV, SRV-1, CMV, SV40, EBV, Herpes saimiri, and parvovirus. Pathology support is an essential core function that enhances colony management and research efforts by a number of institutions and investigators. The Division of Comparative Pathology also trains investigators, technicians, postdoctoral fellows and graduate students in immunohistochemistry methods. AIDS related and non-AIDS related.